title: The importance of the 45 S ribosomal small subunit-related complex for mitochondrial translation in Trypanosoma brucei.
abstract: The mitochondrial 45 S SSU* complex in Trypanosoma brucei contains the 9 S SSU ribosomal RNA, a set of SSU ribosomal proteins, several pentatricopeptide repeat (PPR) proteins, and proteins not typically found in ribosomes, including rhodanese domain protein (Rhod) and a 200-kDa coiled-coil protein. To investigate the function of this complex, PPR29, Rhod, 200-kDa protein, and mitochondrial ribosomal protein S17 were knocked down by RNAi in procyclic T. brucei. A growth retardation phenotype, a reduction in the amount of the 45 S SSU* complexes, and the preferential inhibition of synthesis of the cytochrome c oxidase subunit I over apocytochrome b were observed as early as day 2 postinduction of RNAi. On the contrary, the down-regulation of mitochondrial ribosomal protein L3 drastically reduced the amount of the large subunit and indiscriminately inhibited mitochondrial translation. The relative amounts of translation-competent, long poly(AU)-tailed cytochrome c oxidase subunit I and edited apocytochrome b mRNAs were selectively reduced by ablation of the 45 S SSU* complex. The formation of the 80 S translation complexes, identified by association of the long-tailed mRNAs with the mitoribosomes, was also disrupted. On the other hand, the relative amount of long-tailed edited RPS12 mRNA was not substantially affected, and there was no noticeable effect on the RPS12 translation complexes. In bloodstream trypanosomes, the amount of the 45 S complexes was drastically reduced compared with procyclics. We propose that the 45 S SSU* complex represents a factor required for normal mitochondrial translation that may have selective effects on different mRNAs.
authors.affiliation: From the Department of Biology, University of California, Riverside, California 92521.
authors.forename: Lucie
authors.initials: L
authors.lastname: Ridlon
authors.forename: Ingrid
authors.initials: I
authors.lastname: Škodová
authors.forename: Songqin
authors.initials: S
authors.lastname: Pan
authors.forename: Julius
authors.initials: J
authors.lastname: Lukeš
authors.forename: Dmitri A
authors.initials: DA
authors.lastname: Maslov
mesh_terms: D055785:Gene Knockdown Techniques; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D014176:Protein Biosynthesis / Q000502:physiology*; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D017393:RNA Editing / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016053:RNA, Protozoan / Q000235:genetics / Q000378:metabolism; D012269:Ribosomal Proteins / Q000235:genetics / Q000378:metabolism*; D054679:Ribosome Subunits, Small / Q000235:genetics / Q000378:metabolism*; D014346:Trypanosoma brucei brucei / Q000235:genetics / Q000378:metabolism*
chemical_list: D024101:Mitochondrial Proteins; D046912:Multiprotein Complexes; D015800:Protozoan Proteins; D012333:RNA, Messenger; D016053:RNA, Protozoan; D012269:Ribosomal Proteins
keywords: Leish; Mitochondria; Protein Synthesis; Ribonuclear Protein (RNP); Trypanosoma brucei; Trypanosome